1. Make sure you have the newest version of YSMenu. Grab the TTMenu firmware from the following link (it doesn't contain any fake-killer code whereas other versions might): http://gbatemp.net/index.php?download=2872
2. Unzip the TTMenu archive. Place the "TTMENU" folder onto your microSD card.
3. Unzip the YSMenu archive.
4. Create a folder named "YSMenu" on your microSD card.
5. Place a copy of "TTMENU.DAT" from the official menu into the same folder as the "ttextract.exe" program on your PC. Run "ttextract.exe" on your PC. Place the two resulting files ("ttdldi.dat" and "ttpatch.dat") into the "YSMenu" folder on your microSD card.
6. (a) If you want YSMenu to be your default menu, rename "TTMENU.DAT" from the official menu to "TTMenu.nds" and place it onto the root (top level) of your microSD card. Then place a copy of "YSMenu.nds" onto the root of your microSD card. Then make a copy of "YSMenu.nds" named "TTMENU.DAT" on the root of your microSD card. You should now have "TTMenu.nds", "YSMenu.nds", and "TTMENU.DAT" (a copy of "YSMenu.nds") on the root of your microSD card.
(b) If you want TTMenu to be the default menu, place a copy of TTMENU.DAT from the official menu onto the root (top level) of your microSD card. Then place a copy of "YSMenu.nds" onto the root of your microSD card. Then make a copy of "TTMENU.DAT" named "TTMenu.nds" on the root of your card. You should now have "TTMENU.DAT", "YSMenu.nds", and "TTMenu.nds" (a copy of "TTMENU.DAT") on the root of your microSD card.
7. Optional: place the skin files "YSMenu1.bmp" and "YSMenu2.bmp" (these don't come with YSMenu) into the "YSMenu" folder. You can find a NDS-like skin here: http://gbatemp.net/index.php?download=3082
8. Edit "YSMenu.ini". Place a semi-colon in front of the line that says "LITERALS=LITERALS_JPN". Remove the semi-colon from the line that says "LITERALS=LITERALS_ENG". Save your changes to "YSMenu.ini" and place it into the "YSMenu" folder on your microSD card.
9. Make a new folder named "games" and put a few .nds files in it. Always use the "safely remove hardware" utility before removing your microSD card from your PC. Place the DSTT into the NDS, place the microSD card into the DSTT, and turn on the NDS.

That should be it. If you are using TTMenu as your default, simply run "YSMenu.nds" to get to YSMenu. Otherwise, it should launch directly into YSMenu and you can run "TTMenu.nds" to get back to TTMenu.

When you're done, you should have the following files and folders on your microSD card:

YSMenu.nds (YSMenu)
TTMenu.nds (TTMenu)
TTMENU.DAT (a copy of whichever of the above two you want as your default menu)

YSMENU (YSMenu firmware folder)

YSMenu.ini (YSMenu init file)
ttdldi.dat (extracted from the official loader using ttextract.exe)
ttpatch.dat (extracted from the official loader using ttextract.exe)
YSMenu1.bmp (optional skin)
YSMenu2.bmp (optional skin)

WHERE IS THE DOWNLOAD ?
Go to the link in the first post. Near the top is a link that says "in Japanese" - use it. Search the page (Ctrl-F) for the text "2009/01/01 00:00" (without quotes.) One of the two occurrences of that text is the download link.

Indeed, but it's more of a pity that Yasu's last release saw something like 3 or 4 new R4/TT junky clones hit the market using strictly his soft instead of the people making them actually coding something themselves - not to mention all that crud about someone pretending to be the official R4 folks.